Receding and collapsing tap for threading pipe couplings



July 7, 1931. c. P. WETMORE 1,813,594

RECEDING AND CQLLAPSING TAP FOR THREADING PIPE COUPLINGS 2 Sheet -Sheet 1 Filed March 5 1925 INVENTQR. Q CH/IALES WET/MORE A TTORNEYJ'.

'A July 7, 1931. p, WETMQRE 1,813,594

RECEDING AND COLLAPSING TAP FOR THREADING'PIPE COUPLINGS Filed March 5, 1925 2 Sheets-Sheet 2 A TTORNEYS.

Patented July 7, 1931 UNITED STATES PATENFT OFFI CHARLES P. WET'MORE, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO 0. SMITH COR- PORATION, OF MILWAUKEE, WISCONSIN,.A CORPORATION OF NEW YORK ItEt'flglDING AND COLLAIPSING TAP FOR, THREADING PIPE COUPLINGS Application filed March 5, 1925. Serial No. 13;076.

fic'ally set forth, and the novelty of which I My invention relates tocollapsible taps for threading thetaperlng interior of plpe couplings of large diameter.

It resides in an improved construction of devices whereby the receding radial movements of the thread chasers are controlled by a speed reducing or low speed mechamsm of peculiar type, by the use of which such receding movements are effectuated 3 1' with mathematical precision. A

It resides also in the provision of means operating in conjunction with the speed reducing devices to effect a quick collapse of the thread chasers at the completion of thethreading operation, so as to clear the chasers from their engagement with the coupling and permit the withdrawal ofthe tapping head.

It resides also in the provision of'sensitive feeler devices for contacting with the end of the pipe coupling during the threading operation, which feeler devices are arrahged and connected to control the action of the speed reducing mechanism while the tapping head carrying the thread chasers is advancing into the coupling and threading It resides'also in the provision of automatically operating means for quickly withdrawing the sensitive feeler devices at the moment of collapse, so as to avoid injury to the parts inthe event that the feeding devices for. the tapping head should continue to operate for a moment after the completion of the threading operation.

It resides also in an adjustable timing device byv the setting of which the instant of collapse of the chasers can be predetermined with accuracy. i

It resides also in a hovel angular arranget of the thread chasers in the tapping head, whereb the chasers are stabilized and an improved threading operation is attained and the accumulation of chips is automatically swept out of the flutes in .the tappinghead, so that interference with the action of the chasers is prevented.

It resides further in certain novel features of construction and combinations of elements as Wlll hereinafter be more speciwill be particularly pointed out in the appended claims.

In the drawings accompanying this specification: I

Figure 1 is a longitudinal vertical sec.-

tional view through its central plane showmg the construction and arrangement of the parts embodied in my invention.

Fig. 2 is a transverse sectional view on the line 2-2, Fig. 1, looking in the direction of the arrows, showingin elevation the face of the plate or flange by means of which the tapping mechanism, is supported in position, together with the provision for olding such mechanism against rotation. Fig. 8 is a horizontal sectional View on the line 8-3, Fig. 1, showing a detail of the construction shown in Fig. 2. s

4 is a View in elevation, looking from Fi the gthe'head, of my improved tapping of the said figure, and showing the formation of one element of the timing devices.

Fig. 8 is a view in. elevation showing the cooperating face. of the ad ustable member of the timingdevice.

. Fig. 9 is a View in end elevation, looking from the right of Fig. 1, and showing certain details of construction and arrangement.

Fig. 10 shows diagrammatically the coacting faces of the timing device.

Fig. 11 is a-plan view of a portion of the tapping head. showing the angular arrangement of the chasers, with relation to the center line of the head.

Referring to the details of construction and arrangement shown in the drawings,

the numeral 15 designates one end of a pipe 5 fixed plane, and by such means held in position for interior threading.

The numeral 20, indicates a hollow cylinder designed to be entered in an opening or recess in the tail stock or turret of the lathe,

which cylinder is formed at one end with the tail 23, by engagement a flange 21. By means of the flange, the element 2021 is secured in fixed position by cap screws or bolts passing through openings 22 in the flange, and threaded into stock or turret. The cylindrical body or barrel 23. of the tapping head is reduced in diameter at its rear end, and is seated in the bore of the cylinder 20, a circumferential or other shoulder 24 on the barrel with the face of the flange, forming a ositive stop which limits .the movement 0 the, barrel rearwardly with relation to its mounting. Adjacent the shoulder 24, the barrel is provided upon 25 its surface with opposite longitudinal grooves 25 and 26, forming key seats for lockin keys 27 and 28, which latter are uided \}itn radially extending grooves ormed 1 the front face of the flange 21,

30 such keys being retained in position by cap the same,

screws 29 and 30, passing through the keys and threaded into the said flange. The inner ends of the keys have a width equal to that of the grooves 25 and 26, so as to fill and when so positioned will serve to hold the barrel 23 against rotation, by resisting the countersstrains imposed upon the thread chasers 31 in the rotation of the pipe coupling 15, during the operation of threading the latter.

The rear end ,of the -barrel 23 is threaded. for the reception of a nut 60, which may be formed as a split ring, capable 0 f.adjustment 'to a suitable position upon the said barrel so as to permit a slight radial vibration of the barrel in its bearing, and yet prevent perceptible axialmovement in a forward direction. The parts of the split ring may be clamped in position by, cans of screws 61 and 62, passing through openings in one part and threaded into the other.

The barrel 23 is enlarged at its forward end so as to provide a head 35, in which the chasers 31 in plural number are mounted soas to have movement in slots formed the front end of the head 35, retains the chasers in position in the radial slots and confines them againstaxial movement with respect to the barrel 23. The said barrel is bored out centrally from end to end, the bore being enlarged at the ends of the barrel, for purposes which willbe described hereinafter.

A tubular spindle 40, of less length than helical, slots spindle 40. Asleeve radially therein. A cap 36, attached to the barrel 23, is mounted for both longitudinal and rotary reciprocating movements in the intermediate re uced portion of the bore in the said barrel. At its rear end, the spindle 40 is provided with a circumferential flange 41, one of the purposes of this feature of construction being to eflect the confinement of an expansion spring 42 arranged about the spindle in the enlargement of the bore at the rear end of the barrel 23. One end of the spring rests upon a circular step 43 formed at the inner end of the enlarged bore in the barrel, and the other end bears against. the opposed face of the flange 41, through an anti-friction bearing 44 in rposed between the end of the spring and the flange, to permit free rotation of the spindle 40. Its other purpose will be stated later.

At its other or forward end, the enlarged bore of the barrel 23 receives a cam 45, formed as a cylinder, in the said bore and also in a registering recess formed in the cap 36, fixed upon the head 35 of the barrel. The cam 45 is provided with a plurality of undercut radial grooves, the bottoms of which ta er or incline, corresponding in number an arrangement with the radial grooves formed in the head 35. The chasers 31, which operate radially in the said grooves, are inclined at their inner or bottom ends to correspond with the inclined grooves in the cam' 45,1Ehe

angle of such inclination being about 12, thepurpose of permitting a rapid collapsing movement of the chasers to ta e place when the cam is withdrawn, and at the same time interposing such direct resistance to the inward pressures upon the chasers that the latter are accurately held up to their work and a forced longitudinal retractive move ment of the cam under such pressures is avoided. F

At its rear end, the cam 45 is provided with a coarsely threaded shank 46, which co-acts with the threaded interior of the ad:

'acent end 46 of the tubular spindle 40. 1

diametrihe said spindle is provided with elongated,

cally opposite, parallel-walled,

tending a little more than once, around the s indle. The barrel 23 is provided with iametrically opposite, parallel-walled,

straight guiding slots 49 and 50 of the same a linear extent as the helical slots in the 51, mounted for sliding movement along the barrel 23, supports a transversely arranged pin 52 fixed at its ends in opposite openings in the said sleeve. The

said in is passed through all of the slots in the arrel 23 and the spindle 40, so that when the sleeve 51 is moved along the barrel, a movement of rotation is imparted-to the spindle 40 in the adaptation of the helical slots in the spindle to the fixed position of the pin'52.

47 and 48, each such slots ex;

The sleeve 51 supports a spider 53, the

upon the said sleeve. A threaded engagement between the split hub and the exterior surface of the sleeve, permits a precise ad-' justment of the spider in longitudinal relation to the sleeve to be made. This provision for adjustment is important, inasmuch as the said spider carries the feeler devices which determine the time of the operation of the means for effecting the collapse and recession of the thread chasers. The spider 53 supports forwardly a ring 55, which is provided with a plurality of feelers 56, the latter being adapted to engage the end of the'rotating pipe coupling 15.

The formation 64 upon the outer face of the flange 41 at the rear end of the spindle constitutes a part of the timing mechanism, the said face being transversely notched, as at 65 and 66, such notches being separated by intermediate'fiush projections 67 and 68. A timing dog 69 inthe form of a disc, co-operates with the face 64 of the spindle 40, the'face of the timing dog like t e face 64 being also transversely notched,

' as at 70 and 71, such notches being separated by intermediate flush projections 72 and 73. One notch, as 65 in the part'64 and 70 in the part 69, has a greater width than/the other, and correspondingly, one projection, as 67 .on the part 64 and 72 on the part 69, is wider upon its face than the other. The relative proportions are indicated in the diagrammatic view, Fig. 10. The disk 69 is rovided with opposite arcuate slots 72' and 73 through which extend set screws for securing the same to the end of the barrel 23. The arcuate slots permit a radial adjustment of the disk 69 and thereby enables the relative time -.of collapse. ofthe thread chasers to be regulated.

The chasers 31 may each beof integral construction, or each unit thereof may be in two parts, one of such parts being formed as a'thread cutter 31 and supported upon a base 31 which moves in the radial slots in the head 35. In either construction, the inner end of the chaser will be provided with an inclined lateral rib which is engaged in the undercut inclined slot in the cam operation.

Y sectional plane of the tapping head, instead of being parallel therewith or in the said so that the chaser will bepositively moved radially by a longitudinal movement of the cam in eitherdirection, irrespective of the inward pressure exerted upon the chasers by the coupling 15 during the threading Viewing 4, it will seen that the arrangement of the chasers 31 departs from the usual order of parallelism,an d that such chasers .are disposed at an angle-with relation to the axis and the vertical central plane. I find that the threading operation is facilitated and improved by this arrangement, inasmuch as the chasers are stabilized in a larger degree and the usual chattering attendant upon the older parallel arrangement is obviated. This result I find to be due to thefact that the angular arrangement lengthwise of the chasers, as described, 1 permits the engagement of each chaser to be distributed over a wider section or zone of the coupling at its interior circumferential surface, so that a steadying effectupon the chasers is produced' The width of the section or zone so engaged depends upon the angle at which theradial slots in the tapping head 35 are disposed, and is defined in Fig. 11 by the dotted and projected di- "mensional side lines of the chasers parallel consequence thereof, it was often necessary heretofore to remove these chips by hand. In my invention, the tapping head is selfcleaning, and the accumulation of chips is automatically pushed outwardly and away from the chasers in the angular arrangement of the latter, so that the objections formerly existing are eliminated. The pitch of the threads connecting th spindle 40 and the cam 45, the inclined meeting surfaces of the inner ends of the chasers and the bottoms of the radial slots in the cam, and the pitch of the helical slots in the spindle 40 constituting a speed reducing mechanism possessing a wide range of refinement of action, are all carefully predetermined with relation to the angle and depth of the tapering bore in the coupling 15, so that the receding movement of the chasers as the threading operation proceeds is proportioned with mathematical precision to such tapering bore. The-screw-threaded connection between the spindle and the cam constitutes a swivel by means of which the rotary motion of the spindle is converted into' a longitudinal motion of the cam.

The timing dog 69 is set, as indicated in Fig. 10, with the flush faces of the projections lathe supporting the tapping head is ad-;

vanced until the feelers 56 are in engagement with the end of the coupling. It will be understood that the rotation of the coupling and the automatic feed of the tapping head are synchronized, and that, accordingly such rotating and feeding movements are instituted simultaneously. The engagement of the feelers 56 with the end of the coupling 15, in the manner stated, arrests any further movement of sleeve 51 and the pin 52, while the barrel 23 and tapping head 35, together with the spindle 40, are forced to move forwardly in the feeding movement of the tail stock of the lathe. Consequently, as the barrel 23 moves through thesleeve 51, the pin 52 slides in the straight guiding slots 49 and in the barrel in the advancing movement of the latter, and a slow movement of rotation under perfect control at a greatly reduced speed is imparted to the tubular spindle in the passage of the helical slots 47 and 48 therein over thefixed pin 52, the direction of such rotating movement being indicated by the arrow, Fig. 6. In such rotating movement, the threaded interior end 46 of the s indle takes up the threadon the shank 46 o the cam 45, and gradually withdraws the cam to the rear in aceordancewith a mathematically ascertained rate.

At the moment that the receding chasers 31 have penetrated the bore of the coupling to the depth desired, the spindle 40 has completed so much of its revolution as may be necessary, and the flush faces of the projections on the parts '64 and 69 have cleared themselves from each other. The projections on each part will then be in position to engage by passing into the appropriate notches in the other part, and the spring 42 thus released from confinement, will expand to impart a qui ckened longitudinal movement to the spindle 40, suddenly withdrawingthe cam 45, and effecting the instant ,and complete collapse of the chasers to disengage them from the coupling. The slight accentuated rotation of the spindle which occurs at such time, due to the movement of the inclined walls of the projections and notches of the parts of the timing device over each other in effecting complete engagement, acts to withdraw thefeelers 56 from contact with the end ofthe' coupling and prevents a possible smash, in the event that the-feed over-runs to a slight extent.

The tail stock or turret of the lathe is then run back to withdraw the tapping head from the coupling, and permit removal of the latter from the lathe.

The parts may be restored to normal with the chasers 31 in advanced position by a forward pull of the ring 55. The forward movement of the ring55 effects a reverse rotation of the spindle 40, which in turn effects a reverse movement of the cam 45 and the timing elements so that the'machine is restored to theQinitial operative-condition. This construction permits the'easy disengagement of the parts of the timing devices. The division of the faces .64 and 69 of the timing device permits a balancing of the forces exerted in relatively rotating the said elements to effect their separation and the compression of the spring 42. The purpose in providing the faces with projection of different widths is to obviate engagement of the notches and projections before the spindle 40 has made a proper revolution. With the pin 52 at the extreme left'end of the slots in thebarrel 23 and spindle 40, as shown in Fig. 1, the co-operating faces of the timer assume the separated positions shown in Fig. 10.

It is preferable to provide the barrel 23 with two opposite straight guiding slots, and the spindle 40 with two helical cam slots, with a pin passing through all of the said slots, for the reason that a balancing of the forces exerted in rotating the spindle is thereby attained.

Aspline 75 seated in registering grooves formed in the head 35 and cam 45, serves to align the radial slots formed in the said parts, so that the chasers may be pushed edgewise into the said slots.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States,'is

1. In a collapsible tap, a barrel adapted to be supported at hne end and having a head on the other end thereof, the said head being provided with a plurality of radially extending slots, thread chasers arranged for movement in the said slots, a movable cam in the said head for supporting the chasers in operative position, a spindle provided with helical slots and mounted for rotation in thsaid barrel, a connection between the cam and spindle, and a pin passing through the helical slots, whereby upon movement to advance the tap the spindle is rotated to move the cam and permit recession of the chasers.

2. In a collapsible tap, a barrelprovided I connection between the cain and spindle, and

a pin su ported in a stationary position entering t e helical slots, whereb uponv advancement of the barrel the spindle-is ro-' tated'to move the cam and permit recession of the chasers. I

3. In a collapsible tap, a barrel provided with a plurality of radially extendlng slots,

thread chasers arranged for movement in the said slots, a cam movable in the barrel and supporting the chasers in operative position, a spindle mounted for rotationin I the said barrel and provided with helical i slots, a screw connection between the cam and spindle, and a pin sup orted in a sta tionary position entering t e helical slots,

whereby upon advancement of the barrel the spindle is rotated to move the cam and permlt recession of the bhasers.

- 4. In a collapsible tap, a barrel havin straight slots in opposite sides thereof an i provided also with a plurality of radially ment of the barrel the spindle rotated to I portingl withdraw'the cam to permit recession of the chasers.-

5. In a collapsible tap, a, barrelhaving a strai ht slot in the side thereof and provide at one end with a plurality of radially extending slots, thread chasers arranged for movement in the radial slots, a cam sliding longitudinally in the barrel and sup the chasers in operative position, a spin e provided with a helicalslot about the same, a connection between the cam and spindle, and means as a pin sustained in stationary position entering the straight slot of the barrel and the helical slot of the spindle, whereby in the advancing movement of the barrel the spindle is. rotated to withdraw the cam and permit recession of the chasers.

6: In a receding and collapsible tap, a barrel having a head provided with a plurality of radially extending slots, thread chasers arranged for movement in the. said slots, a cam sliding in the barrel and supporting the chasers in operative position, a spindle mounted for both rotary and longitudinal movements in the barrel, connections between the cam and spindle, means for rotating the spindle to ,move the cam and permit recession of the chasers, and means or moving the spindle longitudinally to effect collapse of the chasers at the termination of the threading operation.

7. In a receding and coll ible tap, a

barrel rovided at one end wit a lurality of rad1ally extending slots, threa .ichasers arranged for movement in the said slots, a

cam sliding in the barrel and supporting the chasers in operative position, a spindlemounted for both rotary. and longitudinal movements in the barrel, connections between the cam andvspindle, meansfor rotating the spindle to withdraw the cam: and

permit recession of the chasers means for v restraining the spindle from longitudinal movement during such recesssion, and means for moving the s indle. longitudinally to effect collapse 0 the chasers at the termination of the threading operation.

8. In a receding and collapsible tap, a

\ barrel provided at one end with a plurality of radially extending slots, thread chasers arranged for movement in the said slots, a cam sliding in the barrel and sup porting the chasers in operative position, a

spindle mounted for both rotary andlongitudinal movements in the barrel connections between the cam and spindle, means for rotating the spindle to withdraw the cam and permit recession of the chasers, means for restrainin thelongitudinal movement of the spin le "during such recession but operative in the rotation of the splndleto release it from such restraint,

and means to move the s'fpindle longitus "spindle mounted for both rotary and longitudinal movements in the barrel, connections between the cam and spindle, means for rotating the spindle to withdraw the cam and permit recession of the chasers,

an expansion springfor imparting longitudinal movement to the spindle, and means for releasing the spring, pressure at the corn clusion of the threading operation to effect collapse of the chasers.

10. In a receding and collapsible tap, a

, barrel provided at one end with a plurality of radially extending slots, thread chasersarranged for movement in the said slots, a

cam sliding in the barrel and supporting the chasers in operative position, a spindle mounted for both rotary and longitudinal movements in the barrel, connections be-' tween the cam and spindle, means for rotating the spindle to withdraw the cam and permit recession of the chasers, an expansion spring confined about the spindle, and means the chasers at for releasing the spring pressure at the termination of the threading operation to ers arranged formovement in ,the said slots to free the spindle and its connecte and supported in operative position by the cam, a rotating spindle connected at one end to the cam, meansfor rotating the spindle to withdraw the cam and permit gradual recession of the chasers, and means for moving the spindle longitudinally to effect collapse of the chasers at the termination of the threading operation. I

12. In a receding and collapsingtap, a barrel havingat one" end a head provided with a plurality of radially extending slots, a cam sliding in the said head,'thread chasers arranged for movement in the said slots and supported in operative position by the cam, a rotating spindle connected at one end to the sliding cam for withdrawing the cam to permit the gradual recession of the chasers, means for moving the spindle longitudinally, and means for restraining such movement, such restraining means comprising devices operative in the rotation of the s indle cam for longitudinal movement to effect collapse of the chasers at the termination of the threading operation. z 13. In a receding and colla sible tap, a barrel provided atone end wit a lurality of radlally extending slots, threa chasers arranged for movement in the said slots,-a cam sliding in the barrel and supporting the chasers in operative position, a spindle mounted for both rotary and longitudinal movements in the barrel connections between the cam and spindle, me us for rotating the spindle to withdraw t e cam and germ1t recession of the chasers, a timing evice for restraining the longitudinal movement of the spindle, and means for effecting such movement when permitted by the timing device to effect collapse of the chasers at the termination of the threading operation.

14. In a receding and rcollapsible tap, a

barrel rovided at one end with a lurality of. radlally extending slots, threa chasers arranged for movement in the said slots, a

,cam sliding in the barrel and supporting the chasers in pperative position, a spindle mounted for both rotary and longitudinal movements in the barrel,: connections between the cam and spindle, means for rotating the spindle to withdraw the cam and 'permlt recession of the chasers, a confined expansion spring for moving the spindle longitudinally, and means for compressing the spring, the last named. said means comprising a timing device operating in the rotation of the spindle to release the spring pressure to move the spindle longitudinally and efiect collapse of the chasers at the termination of the threading operation.

15. In a recedhlg and collapsing tap, a barrel having a head provided wit a plurality of radially extending slots, a cam sliding in the barrel, thread chasers arranged for movement in the said slots and supported inoperative position by the cam, a spindle mounted for both rotary and longitudinal movements in the barrel, means for rotating the spindle to permit a gradual recession of the chasers during the threading operation, and means at the end of the spindle and co-o-peratin means at the end of the barrel for restraining the longitudinal move arranged for movement in the said slots, a

cam sliding in'the barrel and a rotating and longitudinally movable spindle connected to the cam, means for rotating the spindle to efiect separate movement of the cam to pernnt recession of the chasers, means for longitudinally moving jointly the spindle and its connected cam", means for restraining such longitudinal movement, and means for releasing the spindle to the action of its longitudinally sion of the threading operation, such releasing means comprislng a timing device at the end of the spindle and a co-operating part at the end of the barrel, whereby the collapse of the chasers is effected in the joint longitudinal movement of the spindle and cam. t

17. In a 'recedin and collapsing tap, a barrel provided wit a plurality of radially extending slots at one end, a cam sliding in the barrel, thread chasers arranged in the said slots and-supported inoperative position by the cam, a spindle mounted for both rotative and longitudinal nfovements in the barrel and connected at one end to the cam,

means for restraining the longitudinal movement of the spindle in the barrel, means for converting the rotary motion of the spindle while so restrained into a right line motion moving means at the concluof the cam to efiect withdrawal of the latter and permit recession of the chasers during the threading operation, and means operative in the rotation of the spindle to release the restraining means and move the spindle longitudinally to effect colla se of the chas- (am at the conclusion of the threading operation.

18. In a receding imd collapsible tap, a barrel having straight slotted sides and provided also at one end with a plurality of radially extending slots, thread chasers arranged for movement in the said radial slots?" a cam sliding in the barrel, a helically slot-' ted s indle mounted for both rotary and longitu inal movements in the barrel and connected to the cam, a sleeve slidably mounted upon the/barrel 'and'supportin a pin extendingthrough the said straigt and helical slots, means for restraining the movement ofthe sleeve "andpin, means for imparting longitudinal movement to the-spinle, means for restraining longitudinal. movement of h indle whereby the latter is rotated by the pin in the advancing mpvement of the barrel, and means for releasing the spindle in the rotation of the latter to permit its, longitudinal movement to effect collapse of the chasers at the termination of the threading operation.

19. In a collapsible tap, a head provided with a plurality ofv radially extendin slots, thread chasers arranged in the sai slots, a cam sliding in the head for supporting the chasers in operative position, a rotating spindle, a threaded connection between the cam and spindle whereby during the rotation radial slots and supported .by the said cam,a

helically slotted spindle mounted for rotation in the barrel, a contacting feeler device slidably mounted upon the barrel and sustaining in position a pin engaging the straight and helical slots in thebarrel and spindle, whereby in the rlorward movement of the barrel a movement of rotationis imparted to thespindle to withdraw the -cam and permit the gradual recession of the chasers. 21. In a recedin and collapsing tap, a barrel having-its side straight slotted and provided also at one end with a plurality of: radially extendin slots, a cafii sliding in 'the barrel, threa c asers arranged in the radial slots and su orted by the said cam, a helically slotted spindle mounted for rotation in the barrel, a contacting feeler device slidably mounted upon the barrel and sustaining in position a pin. engaging the straight and helical slots in the barrel and spindle, whereby in the forward movement of the barrela movement of rotation is imparted to the spindle to withdrai'v the cam and permit the-gradual recession of the chasers, and means for movin the spindle longitudinally to efiect the co lapse of the chasers at the conclusion of the threading operation.

22. In a recedi and collapsing tap, a

'1 barrel having its side straight slotted and provided also at oneend with'a plurality of radiallyextending slots, a cam sliding in the barrel, thread chasers arranged in the radial slots andsu ported by thesaid cam, a helically slotte spindle mounted for rotation in the barrel, a contactin fe'eler device slidably mounted-upon the fiiarrel and sustaining in position a pin engaging the strai ht and helical slots in the barrel and spindle, whereby in the forward movement of the barrel a movement of rotation is imparted to the spindle to withdraw the cam and permit the gradual recession of the chasers, means for movin the spindle longitudinally to eifect the col apse of the chasersat the conclusion of the threading operation, 7

and means to retract the feeler device by a reverse rotation of the spindle.

.23. In. a receding and colla sing tap, a I

barrel provided at one end wit a plurality of radially extendin slots, a cam sliding in the barrel, thread 0 asers arranged in the said slots and supported inoperative position by t e said cam, means for withdrawing the cam to permit the gradual recession of the chasers durin the threading operation, such means vinclu ing a rotating and lon tudinally movable spindle disposed in t e barrel and connected at one end to the cam and 'provided at the other end with projections and notches, and a timing dog mounted upon the other end of the barrel and provided with co-operating projections and notches, and means for moving the spindle lon 'tudinally when opposing pro'ections an notches engage to im art ad itional movement to the cam and e ect collapse of the chasers at the conclusion of.the threading operation.

24. In a receding and collapsing tap, a I

barrel provided at one end with a plurality of radiall extending slots, a cam sliding in the barre thread chasers arranged in the said slots and supported-in o erative position by the said cam, means or withdraw ing the cam to permit the gradual recession of the chasers during-the threading operation, such means including a rotating and longitudinally movable spindle disposed in the barrel and connected at one end to the cam and provided at theother end with projections/and notches, and a timin dog mounted upon the other end of the Iarrel and provided. with co-operating projections and notches,. and means for moving the spindle longitudinally when opposing projections and notches engage to, impart addi-.

tional movement to the cam and efiect collapse of. the chasers at the conclusion of the threadingl-operation, the said projections and notches aving inclined walls to cause a; slight further rotation of the spindle at the time of engagement, and to balance th forces of rotation in efiecting their separa tion and restoration to normal position.

25. In a receding and collapsing tap, a barrel having a tapping head provided with radially movable thread chasers, retractable means in the head for supporting the said chasers in operative pos1t1on, a rotating spindle operatively connected at one end to said means, means for rotating the spindle to effect withdrawal of the chaser supporting meansand permit the gradual recession of the chasers during the threadin operation, means sliding on the barrel an connections therefrom 'to the spindle rotating means for reversing the rotation of the said spindle to restore the chasers to their initial position.

26. In a collapsible tap, a head, a plurality of relatively movable thread chasers ar- 4 ranged in said head, amovable cam for supporting said chasers in operative position o and for efiecting a radial movement thereof, a rotatable spindle, means responsive to the 1 relative feeding movement of the thread chasers and the article to be threaded for, rotatin said spindle,-and connections between tlie cam and the spindle, said connections including means for efiecting-a linear 1 movement of said cam during the rotation of the spindle. J T? p 27. In a collapsible tap, a head provided with a plurality of radially extending slots,

radially movable thread chasers arranged therein, a sliding cam for supporting said chasers in operative position and for eflecting a radial movement thereof, a rotatable a5 spindle, means responsive to the relative feeding movement of the thread chasers and the article to be threaded for rotating said spindle, and connections between the cam and the spindle, said connections including means for effecting a sliding movement of the cam during the rotation of the spindle. t

28. In a col apsible tap, a head provided with a pluralit of radially extendmg slots, radially mova le thread chasers in said slots, a sliding cam for supporting the chasers in operative position and for eflec'tin a radial movement thereof, a rotatable spindle, means responsive to the relative feeding movement of the thread chasers and the 5 article to be -threaded for rotating said spindle, and a screw thread connection between the cam and the indle whereby rotation of the latter will i i ect a sliding movement of the cam. r 5a In testimony whereof, I have signed my name at Milwaukee, Wisconsin, this.28.th day of February, 1925. r a C. 1?. WETMORE. 

